Indirect boiling for water treatment

ABSTRACT

Systems and methods relate to vaporizing water into steam, which may be utilized in applications such as bitumen production. Initial indirect vaporization of the water at a first pressure for treatment precedes a steam generator boiling the water at a second pressure higher than the first pressure. The indirect vaporization of the water occurs in a vessel upon contact of the water with a substance such as solid particulate heated to a temperature sufficient to vaporize the water. Impurities in the water deposit on the solid particulate and/or combust limiting pass through of the impurities to the steam generator given that a vapor output of the vessel from the initial indirect vaporization condenses and is pressurized before being supplied to the steam generator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application which claims benefit under 35 USC §119(e) of and priority to U.S. Provisional Application Ser. No. 61/888,576 filed 9 Oct. 2013, entitled “INDIRECT BOILING FOR WATER TREATMENT,” which is incorporated by reference herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None.

FIELD OF THE INVENTION

Embodiments of the invention relate to methods and systems for generating steam which may be utilized in applications such as bitumen production.

BACKGROUND OF THE INVENTION

Several techniques utilized to recover hydrocarbons in the form of bitumen from oil sands rely on generated steam to heat and lower viscosity of the hydrocarbons when the steam is injected into the oil sands. One common approach for this type of recovery includes steam assisted gravity drainage (SAGD). The hydrocarbons once heated become mobile enough for production along with the condensed steam, which is then recovered and recycled.

Costs associated with building a complex, large, sophisticated facility to process water and generate steam contributes to economic challenges of oil sands production operations. Such a facility represents much of the capital costs of these operations. Chemical and energy usage of the facility also contribute to operating costs.

Past approaches rely on once through steam generators (OTSGs) to produce the steam. However, boiler feed water to these steam generators requires expensive de-oiling and treatment to limit boiler fouling problems. Even with this treatment, fouling issues persist and are primarily dealt with through regular pigging of the boilers. This recurring maintenance further increases operating costs and results in a loss of steam production capacity, which translates to an equivalent reduction in bitumen extraction.

Therefore, a need exists for methods and systems for generating steam that enable efficient hydrocarbon recovery from a formation.

BRIEF SUMMARY OF THE DISCLOSURE

In one embodiment, a method of treating and vaporizing water includes circulating a solid particulate in a vessel and heating the solid particulate. Treating the water includes contacting the water with the solid particulate heated to a temperature for vaporizing the water into steam, which is at a first pressure and is then separated from the solid particulate and condensed into a liquid to form a treated feed. The method further includes vaporizing the treated feed to generate steam at a second pressure higher than the first pressure.

For one embodiment, a system for treating and vaporizing water includes a vessel with a fluidized bed of circulating solid particulate, a heat source to transfer thermal energy to the solid particulate, an inlet for the water into the vessel to contact the water with the solid particulate heated to a temperature for vaporizing the water into steam that is at a first pressure, and an outlet of the vessel in which the steam flows separated from the solid particulate. A cooler couples to the outlet to condense the steam into a liquid providing a treated feed. A steam generator vaporizes the treated feed and outputs resulting steam at a second pressure higher than the first pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and benefits thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic of a system including a fluidized bed for initial vaporization to treat water fed into a steam generator operated at injection pressure, according to one embodiment of the invention.

FIG. 2 is a schematic of an exemplary system with input into a riser for the initial vaporization to treat the water, according to one embodiment of the invention.

DETAILED DESCRIPTION

Turning now to the detailed description of the preferred arrangement or arrangements of the present invention, it should be understood that the inventive features and concepts may be manifested in other arrangements and that the scope of the invention is not limited to the embodiments described or illustrated.

Embodiments of the invention relate to systems and methods for vaporizing water into steam, which may be utilized in applications such as bitumen production. Initial indirect vaporization of the water at a first pressure for treatment precedes a steam generator boiling the water at a second pressure higher than the first pressure. The indirect vaporization of the water occurs in a vessel upon contact of the water with a substance such as solid particulate heated to a temperature sufficient to vaporize the water. Impurities in the water deposit on the solid particulate and/or combust limiting pass through of the impurities to the steam generator given that a vapor output of the vessel from the initial indirect vaporization condenses and is pressurized before being supplied to the steam generator.

FIG. 1 illustrates a system for recovering hydrocarbons that includes at least one production well 100 and at least one injection well 102. In an exemplary embodiment, the injection well 102 and the production well 100 provide a well pair for a steam assisted gravity drainage (SAGD) operation. Various other thermal oil recovery operations including cyclic steam stimulation, solvent aided SAGD and steam drive may also employ processes described herein.

In operation, a steam chamber develops as steam is introduced into a formation through the injection well 102 and a resulting petroleum fluid of steam condensate and the hydrocarbons migrates through the formation due to gravity for recovery with the production well 100. The steam comes from water treated as described herein using a vessel 104 and supplied to a steam generator 106. The steam contacts the hydrocarbons such that heat transfers upon condensation making the hydrocarbons mobile and enabling gravity drainage thereof.

For some embodiments, the water recycled and treated for steam generation may come from blown-down liquid waste produced during steam generation and/or from separated production fluid associated with the SAGD bitumen recovery operation. A production separator 108 thus receives the production fluid to remove the hydrocarbons from the water. The water output from the production separator 108 passes to the vessel 104.

The water at time of being vaporized in the vessel 104 for treatment may still contain: at least about 1000 parts per million (ppm), at least 10,000 ppm or at least 45,000 ppm total dissolved solids; at least 100 ppm, at least 500 ppm, at least 1000 ppm or at least 15,000 ppm organic compounds or organics; and at least 1000 ppm free oil. This initial vaporization and then condensation may provide the only treatment of the water relied on preceding steam generation for injection and may feed to a steam generator 106 water containing less than 1000 ppm or less than 100 ppm total dissolved solids; less than 100 ppm or less than 50 ppm organic compounds or organics; and less than 1000 ppm or less than 100 ppm free oil.

The vessel 104 contains solid particulate. As used herein, examples of the solid particulate include geldart A solids, geldart B solids or any mixture thereof. Exemplary geldart A or B solids include sand, metal spheres, cracking catalyst and mixtures thereof. In some embodiments, fluidization of the solid particulate keeps the solid particulate moving within the vessel 104 during operation to vaporize the water. Such fluidization may involve circulation of the solid particulate and may rely on addition of supplemental steam.

The vessel 104 further couples to a heat source that may include a supply of oxidant, such as air or oxygen, and fuel, such as natural gas or methane. The oxygen and fuel introduced into the vessel 104 combusts to heat the solid particulate such that the water introduced into the vessel 104 vaporizes upon contact with the solid particulate. During such combustion, contaminants, such as organic compounds deposited on the solid particulate from the water, may partially or fully convert into carbon dioxide and water, and some salts deposited on the solid particulate from the water may come off and be swept out of the vessel 104.

Surface area of the solid particulate provides enough dispersion of the deposits to limit heat transfer interference. As needed over time, replacing some or part of the solid particulate may ensure desired performance is maintained at minimal cost and with limited to no interruption. For example, a lockhopper system employed with embodiments can enable such withdrawal and replacement while in continuous operation.

The vessel 104 operates at a pressure between atmospheric pressure and less than a desired injection pressure of the steam into the injection well 102. These pressures limit compression needs with respect to the fuel and oxidant supplied to the vessel 104. In some embodiments, the pressure in the vessel 104 ranges between 0 and 350 kilopascals (kPa), 0 and 700 kPa, 0 and 5000 kPa or less than 1000 kPa. A gaseous outlet 112 of the vessel 104 thus conveys water vapor at a corresponding pressure mixed with combustion exhaust. The water vapor exits the vessel 104 through the gaseous outlet 112 while the solid particulate remains in the vessel 104 and/or is trapped by filters or cyclones, for example.

A condenser or heat exchanger 114 couples to the gaseous outlet 112 of the vessel 104 and cools the water vapor into a liquid. A treatment separator 116 receives flow from the heat exchanger 114 for removal of gases, such as the combustion exhaust, from the water that a pump 118 then pressurizes for feeding to the steam generator 106. The pump 118 may pressurize the water to above 6500 kPa such that the steam conveyed to the injection well 102 is at the desired injection pressure. For efficiency, heat exchange may preheat the water from the treatment separator 116 prior to being supplied to the steam generator 106.

An example of the steam generator 106 includes an economical and efficient package drum boiler, which has stringent feed impurity limits that may not be practical to achieve with prior water treatment options. Other types of the steam generator 106 suitable for use include a once through steam generator or direct steam generator. Regardless of operational configuration of the steam generator 106, limiting the feed impurities with use of the vessel 104 for water treatment can reduce fouling issues and blown-down waste liquid.

In some embodiments, the drum boilers used for the steam generator 106 enable locating the steam generator 106 at a remote well pad or within 100 meters of the injection well 102. Large scale and complex steam generation approaches depend on producing the steam at a central processing facility. However, heat loss in steam delivery lines from the central processing facility to the remote well pad limits length of such lines.

Various options exist for adding makeup water if necessary. In some embodiments, additional water 110, such as saline source water, combines with the water from the production separator 108. For some embodiments, the additional water 110 may first be treated by reverse osmosis, for example, and heated to provide steam, which is at a pressure corresponding to the pressure of the water being supplied to the vessel 104 and in which the steam is combined for preheating thereof. Such preheating of the water to the vessel 104 may enable limiting capital costs associated with the vessel 104.

The makeup water may further bypass the vessel 104. In some embodiments, flow from the steam generator 106 combines with another steam source 120 at a corresponding pressure for introduction of the steam into the injection well 102. For example, saline source water may pass through treatment, such as reverse osmosis, and then be pressurized and boil to provide the steam source 120.

FIG. 2 shows an alternative system with input of water into a riser 205 forming part of a heating vessel 204 for the initial vaporization to treat the water that is recovered from a production well 200 and removed from oil with a production separator 208. Solid particulate circulates through the riser 205 and the heating vessel 204. Similar to the system in FIG. 1, reactants for combustion enter the heating vessel 204 and are ignited in order to regain thermal energy used to vaporize the water.

Flue gases from the combustion exit the heating vessel 204 through an exhaust following any filtering to retain the solid particulate. Light gases that can dissolve in the water thereby separate out. Limiting conveyance of these gases with the vaporized water may facilitate controlling acidity of the water and may not rely on downstream separation following condensing of the vaporized water.

The solid particulate heated in the heating vessel 204 transfers to the riser 205 where the water contacts the solid particulate resulting in vaporizing the water. The vaporized water provides lift for the solid particulate in the riser 205. The solid particulate once up the riser 205 then settles and returns by gravity to the heating vessel 204 since the heating vessel 204 is disposed below a top of the riser 205. The vaporized water exits the riser 205 at a gaseous outlet 212.

A heat exchanger 214 couples to the gaseous outlet 212 of the riser 205 and cools the water vapor into a liquid. A pump 118 receives flow from the heat exchanger 214 and pressurizes the water then supplied to a steam generator 206. The pump 218 may pressurize the water to above 6500 kPa such that the steam from the steam generator 206 conveyed to an injection well 102 is at the desired injection pressure.

Configurations to provide for the indirect vaporization of the water in order to treat the water may employ further attributes as described in the following patent applications: U.S. application Ser. No. 13/547,565, entitled “Indirect Steam Generation System and Process” filed Jul. 7, 2012; U.S. Application Ser. No. 61/737,973, entitled “Heating for Indirect Boiling” filed Dec. 17, 2012; U.S. Application Ser. No. 61/737,948, entitled “Water with Solvent Indirect Boiling” filed Dec. 17, 2012; and U.S. Application Ser. No. 61/737,967, entitled “Heat Exchange for Indirect Boiling” filed Dec. 17, 2012. Each of the aforementioned patent applications is hereby incorporated by reference in their entirety. In particular, these patent applications describe indirect vaporization at the injection pressure but may be applied as described herein to vaporize and condense water for treatment while at pressures less than the injection pressure with subsequent steam generation using the water from such treatment at the injection pressure.

Although the systems and processes described herein have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the invention as defined by the following claims. Those skilled in the art may be able to study the preferred embodiments and identify other ways to practice the invention that are not exactly as described herein. It is the intent of the inventors that variations and equivalents of the invention are within the scope of the claims, while the description, abstract and drawings are not to be used to limit the scope of the invention. Each and every claim below is hereby incorporated into this detailed description or specification as additional embodiments of the present invention. The invention is specifically intended to be as broad as the claims below and their equivalents. 

1. A method of treating and vaporizing water, comprising: circulating a solid particulate in a vessel; heating the solid particulate; treating the water by contacting the water with the solid particulate heated to a temperature for vaporizing the water into steam that is at a first pressure and is then separated from the solid particulate and condensed into a liquid to form a treated feed; and vaporizing the treated feed to generate steam at a second pressure higher than the first pressure.
 2. The method according to claim 1, wherein the heating the solid particulate is by combusting fuel inside the vessel.
 3. The method according to claim 1, wherein the first pressure is less than 1000 kilopascals.
 4. The method according to claim 1, wherein the first pressure is less than 5000 kilopascals and the second pressure is at least 6500 kilopascals.
 5. The method according to claim 1, wherein the heating includes supplying oxygen to the vessel to burn off organics from the water that are deposited on the solid particulate.
 6. The method according to claim 1, wherein the water contacts the solid particulate in a riser such that the vaporizing provides lift for transporting the solid particulate up the riser for gravity return to the vessel.
 7. The method according to claim 1, wherein the solid particulate includes at least one of geldart A solids and geldart B solids.
 8. The method according to claim 1, further comprising injecting the steam at the second pressure into a formation and producing steam condensate separated from recovered hydrocarbons to form the water that is contacted with the solid particulate.
 9. The method according to claim 1, wherein the water that is contacted with the solid particulate comes from blown-down liquid waste produced during steam generation.
 10. The method according to claim 1, further comprising separating combustion gases used in heating the solid particulate from the treated feed.
 11. The method according to claim 1, wherein combustion gases used in heating the solid particulate are exhausted without mixing with the steam produced by the water contacting the solid particulate.
 12. A system for treating and vaporizing water, comprising: a vessel with a fluidized bed of circulating solid particulate; a heat source to transfer thermal energy to the solid particulate; an inlet for the water into the vessel to contact the water with the solid particulate heated to a temperature for vaporizing the water into steam that is at a first pressure; an outlet of the vessel in which the steam flows separated from the solid particulate; a cooler coupled to the outlet to condense the steam into a liquid providing a treated feed; and a steam generator to vaporize the treated feed and output resulting steam at a second pressure higher than the first pressure.
 13. The system according to claim 12, wherein the heat source includes a fuel and oxidant supply coupled to the vessel for heating the solid particulate by combustion.
 14. The system according to claim 12, wherein the first pressure is less than 1000 kilopascals.
 15. The system according to claim 12, wherein the first pressure is less than 5000 kilopascals and the second pressure is at least 6500 kilopascals.
 16. The system according to claim 12, further comprising a riser in which the water contacts the solid particulate such that the vaporizing provides lift for transporting the solid particulate up the riser for gravity return to the vessel.
 17. The system according to claim 12, wherein the solid particulate includes at least one of geldart A solids and geldart B solids.
 18. The system according to claim 12, further comprising: an injection well coupled to the steam generator for introducing the steam at the second pressure into a formation; and a production well coupled to a separator that removes steam condensate from recovered hydrocarbons to provide the water that is contacted with the solid particulate.
 19. The system according to claim 12, further comprising a separator for removing combustion gases used in heating the solid particulate from the treated feed.
 20. The system according to claim 12, further comprising an exhaust from the vessel for removing combustion gases used in heating the solid particulate without mixing of the gases with the steam produced by the water contacting the solid particulate. 